Sex Differences in Lopinavir Concentrations and Occurrence of Marked QTc Prolongation Episodes in Patients with COVID-19.

Dear Editor,

We read with interest the article of Zekarias et al. [1] on sex-related differences to adverse drug reactions (ADRs) in patients with COVID-19. The authors extracted case safety reports from VigiBase, and found that there were more reports on hydroxychloroquine (HCQ, 864 reports) and lopinavir/ritonavir (LPV/r, 309) in male patients than in female patients (HCQ 612 and LPV/r 160, respectively). The most commonly reported ADRs were similar for female and male subjects except for the prolonged QT interval, which was documented in 31% of male reports and 19% of female reports (p = 0.01). This sex-related difference on QT interval prolongation is in contrast to what has been reported in the literature, as this event typically occurs more frequently in female patients than it does in male patients [1]. We support the authors’ findings with our prospectively collected data and provide a scientific rationale for the sex difference related to both the clinical course of COVID-19 and the occurrence of ADRs.

We previously investigated the effect of a systemic inflammatory response to SARS-CoV-2 on LPV and HCQ plasma concentrations in patients admitted to the University Hospital in Basel between 25 February and 30 April, 2020 [2]. Patients received LPV/r for 5–7 days combined with HCQ for 2 days [2]. For the present study, we specifically investigated sex differences in plasma concentrations of the cytochrome P450 (CYP) 3A4 substrate LPV and the occurrence of corrected QT (QTc) prolongation episodes in the same COVID-19 cohort. Lopinavir plasma trough concentrations were routinely measured 2 or 3 days after initiating treatment and an electrocardiogram was performed at admission and repeated 3 days after. Additional electrocardiogram measurements were performed as clinically indicated. A marked QTc prolongation episode was defined as a QTc interval > 500 ms, a threshold known to increase the risk of life-threatening cardiac events, and to predict short-term mortality independent of comorbidity [3].

The study population consisted of 92 patients with COVID-19, of those 65 (71%) were male and 27 (29%) were female [2]. Male and female patients had a median (interquartile range) age of 59 (47–70) and 59 (52–65) years, respectively. Clinical laboratory parameters were comparable in male and female patients. There was a trend towards higher median LPV trough concentrations in male compared with female patients (27.2 vs 20.6 µg/mL, p = 0.09). When categorizing female patients by age group to reflect hormonal changes related to menopause, the median LPV trough concentrations were not different in female patients aged ≥ 50 years compared to male patients, irrespective of age (26.3 vs 27.2 µg/mL, p = 0.44). However, female patients aged < 50 years had significantly lower LPV concentrations compared with male patients (19.0 vs 27.2 µg/mL, p = 0.01). Lopinavir concentrations were not significantly different in male patients aged < 50 and ≥ 50 years (Fig. 1). Marked QTc prolongation episodes were not observed in patients aged < 50 years (n = 23). Among patients with COVID-19 aged ≥ 50 years and in the absence of an electrolyte imbalance or concomitant drug with a QT prolongation risk (other than LPV and HCQ), the proportion of patients with a QTc interval of ≥ 500 ms was approximately three times higher in male than in female patients (12.5% [6/48] vs 4.8% [1/21]). Furthermore, male patients had higher QTc prolongation intervals as indicated in Table 1. There were no events of torsade de pointes.

Fig. 1

Box plots (showing the 5th, 25th, 50th, 75th, and 95th percentiles) of lopinavir plasma trough concentrations according to sex. Female and male patients were further categorized by age < 50 years and ≥ 50 years

Table 1

Actual corrected QT (QTc) values in seven study participants with marked QTc prolongation episodes

Sex	Age (years)	QTc (ms)
Male	77	525
Male	50	523
Male	60	503
Male	59	515
Male	81	523
Male	82	512
Female	52	507

ms milliseconds

COVID-19 shows a sex disparity in its clinical outcome. While the number of male and female patients contracting COVID-19 appears to be similar, more severe disease and a higher mortality rate are observed in male compared with female patients, even after adjusting for coexisting comorbidities. The observed difference is likely related to biological determinants. The X-chromosome contains a high density of immune-related genes involved in both the innate and adaptive responses [4]. Female patients are less susceptible to many infections, and hence, have an immunological advantage over male patients [4]. This phenomenon has also been associated with less severe courses of viral infections in female patients. Hormones may explain the observed sex disparity in the course of COVID-19. Estradiol downregulates the angiotensin-converting enzyme 2 (ACE2), the entry receptor of SARS-CoV-2 [5]. Levels of estradiol were shown to be negatively correlated with the pro-inflammatory cytokine interleukin-6 (IL-6) [6]. Elevated IL-6 levels inhibit drug metabolism mediated by CYP3A4 resulting in high drug concentrations [2]. Furthermore, inflammatory cytokines increase the risk of QT interval prolongation and life-threatening arrhythmias owing to their electrophysiological effects on the myocardium [7]. These considerations led us to hypothesize that male patients with COVID-19 are more likely to present with elevated drug plasma concentrations and cardiac adverse events. We demonstrated a sex difference in median LPV trough plasma concentrations, with concentrations 30% lower in female patients aged <50 years compared with male patients. This observation is in agreement with the fact that pre-menopausal female patients have high estradiol levels, lower IL-6 plasma levels [6], and consequently less inhibition of CYP3A4 metabolism and lower drug concentrations [2]. However, we were unable to investigate the precise menstruation cycle in our female COVID-19 patient population. Importantly, higher plasma concentrations of narrow therapeutic index drugs in male patients and post-menopausal female patients raise the concern of an increased risk of ADRs and a higher magnitude of drug–drug interactions with medications whose metabolism is inhibited by LPV/r [2]. Our analysis showed that male patients with COVID-19 were more likely to present with a marked prolongation of the QTc interval than female patients. This finding goes alongside the finding of Zekarias et al. [1].

In addition to the inhibition of CYP3A4 metabolism and the related high drug concentrations, ADR cascade, other factors may contribute to the observed frequency of a prolonged QT interval in male patients. High IL-6 levels in male patients lead to direct myocardial injury [7]. Furthermore, ACE2 is expressed both in the lung and heart tissues, thus downregulation of ACE2 by estradiol [5] may decrease the risk of cardiac inflammation and associated QT interval prolongation in female patients. Because of the immunomodulatory effect of estradiol, it has been suggested that the hormone per se or in combination with antivirals may represent a viable therapeutic option for COVID-19. Of interest, pre-menopausal female patients were shown to have a milder course of COVID-19, better outcomes, and shorter hospitalization times than menopausal female patients [6]. Estradiol is currently being evaluated in a clinical trial to reduce the severity of symptoms in patients with COVID-19 (NCT04359329).